1. Field of the Invention
The present invention relates to a method and an apparatus for forming a three-dimensional laminated product, such as, a model or core useful for investment casting of an intended ornamental jewelry craft product.
2. Description of the Related Art
In recent years, it has been known to form a three-dimensional product by successively superposing a number of photo-cured laminae of stratified cross sections of the three-dimensional product one on the top of another. Specifically, a photo-cured lamina is formed on previously photo-cured laminae by scanning and curing a specified thickness of surface layer of a photo-curable liquid by laser energy, building up the three-dimensional product. One of such methods and apparatus for forming three-dimensional products from a photo-curable liquid is known from, for instance, Japanese Unexamined Patent Publication No. 56-144478.
In order to introduce a fresh liquid of a quantity necessary to provide a specified thickness of surface layer of the photo-curable liquid, which will to be formed as a photo-cured lamina on the previously superposed photo-cured laminae, the under-building product needs to be moved precisely by a distance equal to the specified thickness in progress steps away from the working surface level of the photo-curable liquid at which a surface layer of the fresh liquid is irradiated with laser energy. In practice this has proven difficult. For example, for forming the surface layer of the photo-curable liquid with a precisely controlled thickness, as described in, for instance, European Patent Specifications EP 0171069B1 and EP 0535720B1, the under-building product is initially moved down away from the specified working surface to a level beyond the specified working surface level, and then, moved back to the specified working surface level in order to accomplish each stepwise adjustment during the process of making the article being built. Alternatively, as described in, for instance, Japanese patents Nos. 26195445 and 2715649, a fresh liquid spray mechanism is provided to spray a fresh liquid so as to form a precise thickness of surface layer of a photo-curable liquid on an under-building product after moving down the under-building product away from the specified working surface by a distance equal to the specified thickness.
While employing an initial increment of movement of the last formed lamina away from the specified working surface to a level beyond the specified working surface level enables the apparatus for building a three-dimensional product by photo-curing to be simple in construction and mechanism and compact in overall size, however, it causes a somewhat tangled problem of spending a long time before completely building a three-dimensional product. That is, the photo-curable liquid is governed in fluidity by its relatively high viscosity and surface tension, and therefore, a relatively long time is required to introduce a precisely controlled quantity of the fresh liquid for providing a specified thickness of surface layer of the photo-curable liquid for the next processing step. In addition to a long time that is spent before introduction of a precisely controlled quantity of the fresh liquid, a time is required to move back the working surface to the specified working surface level after the introduction of a precisely controlled quantity of the fresh liquid. Further, application of laser energy onto a surface layer of the photo-curable liquid must wait for a time until the surface layer is entirely leveled. In consequence, a long working time is necessary to complete a single photo-cured lamina, which causes a rise in manufacturing costs. Since the photo-curable liquid transforms from a fluid to a solid by means of photo-chemical reaction, such as, a radical reaction and a cationic reaction, the photo-curable liquid itself has a somewhat restricted effective life, which causes a large quantity of photo-curable liquid of no direct use, and hence leads to a rise in manufacturing costs.
On the other hand, while spraying a fresh liquid by means of the fresh liquid spray mechanism to form a precise thickness of surface layer of a photo-curable liquid on an under-building product reduces a time required to introduce a precisely controlled quantity of the fresh liquid and level a surface layer, and realizes miniaturization of a fluid container in which the photo-curable liquid is accommodated, the fresh liquid spray mechanism has to be equipped not only with various associated parts such as a nozzle, mesh screen, a rotary shaft, a brush and a water wheel which makes the apparatus bulky, but also a secondary fluid container in which a photo-curable liquid to be sprayed must be provided. Further, there is the necessity of installing a surface level adjusting mechanism for adjusting a level of the surface layer after spraying a fresh liquid. Such a surface level adjusting mechanism is complicated in structure and expensive, which leads to a rise in manufacturing costs.
It is a primary object of the invention to provide a method an apparatus for forming a three-dimensional laminated product from a photo-curable liquid by step-wise photo-curing of laminae.
Another object of the invention is to provide a three-dimensional laminated product forming apparatus equipped with a liquid surface leveling device working as a capillary which draws up a reserve of photo-curable liquid therein and applies it over a laminated product that is being built up so as to form a uniform thickness of a surface layer of the photo-curable liquid with a working surface leveled and smoothed.
The foregoing objects are accomplished by providing a three-dimensional laminated product forming method and apparatus for forming a three-dimensional laminated product from a photo-curable liquid by progressively superposing solid laminae having a specified thickness, one on top of another, each solid lamina being provided by photo-curing a surface layer of the photo-curable liquid and converting it to a solid lamina. The three-dimensional laminated product forming apparatus comprises a product table on which a three-dimensional solid product is built up in progressive steps, said product table being sunken in a reservoir of photo-curable liquid by a distance equal to the specified thickness of the solid lamina in each said step; and a liquid surface leveling device which works with a capillary effect to collect or draw up a reserve of photo-curable liquid while it is in contact with the surface of the photo-curable liquid contained in a container which is placed on a container table. The leveling device is moved over the surface of the photo-curable liquid to apply the collected photo-curable liquid over a three-dimensional laminated product, that has been partly built up on a product table and stepped down for the next lamina, so as to form a uniform thickness of a surface layer of the photo-curable liquid with a surface leveled and smoothed over the three-dimensional laminated product that has been partly built up. An irradiating head forms a beam spot of reactive stimulation (ultraviolet energy) on the smoothed and leveled surface layer of the photo-curable liquid so as thereby to cure the surface layer, and convert it to a solid lamina superposing on the three-dimensional laminated product that is partly built up as the three-dimensional laminated product.
According to the three-dimensional solid product forming apparatus and method, it is enabled to form a specified thickness of a surface layer of a photo-curable liquid over a three-dimensional product having been partly building up. The surface layer leveling device comprises a pair of surface leveling blades having an entrance that is set for a predetermined opening so that it is arranged as to work as a capillary. The structure is simple and the driving mechanism for it is also simple and inexpensive. As a result, the three-dimensional solid product forming apparatus is made small in overall size, operates quickly and is provided at low cost.